[disclosure: I'm a personal friend of the author of this article.]
I lived in Montreal for three years, or four winters, depending upon how you count.
I believe that Montreal has the most important element necessary to become an open-source startup hub, namely a lot of good talent. The language barrier exists, but is not strong enough that it has hindered any open-source efforts in Montreal (as far as I've seen).
The main hurdle to Montreal becoming any sort of startup hub is cultural. IMHO, Montrealais are not very opportunistic in starting and pursuing business.
I don't think this is Montreal-specific in any way, many cities are like this.
I think people are inspired most of all by other people they meet in their day-to-day lives, not images on TV or in media. The current difficulty is that Montrealais have very few positive role models around them, to show how it's done. In SF or NYC, you could easily move in a social circle that contains a successful business entrepreneur. "Oh, if he could do it, then I can do that too!" But most people in Montreal don't happen to know a successful tech entrepreneur, not even as an acquaintance in passing.
Note that I have found that Montrealais ARE very opportunistic when it comes to social entrepreneurism. Witness social events The Strip Spelling Bee http://stripspellingbee.blogspot.com/ (and other productions by Perpetual Emotion Machine Productions, like Slow Dance Night), musical innovation particularly in low-fi and DIY subgeneres, and non-profit activism like Head and Hands.
But business ambition is regarded with skepticism at best, and is generally considered a form of elitism and lack of social consciousness.